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Germanate tellurite glasses doped with Eu3+ and Tb3+ were synthesized by the conventional melt-quenching method. There is no indication of the energy transfer between dopant ions in this host, but the co-dopants exhibit excellent color purity of 100% for Eu3+ and 80% for Tb3+. The co-doped glass exhibits yellow luminescence. The quantum yield of the Eu3+ emission is equal to 23% under 395 nm excitation. The thermal quenching of Eu3+ and Tb3+ luminescence occurs at different temperature ranges, which enables the thermal sensing properties of the material. The relative fluorescence intensity ratio (FIR) sensitivity of 0.16% K−1 was recorded in the wide range of temperatures spanning from −193 °C up to 0 °C. The temperature dependence of the decay times was also studied. The lifetime-based temperature sensitivity was determined to be 0.95% K−1 at 250 °C for Tb3+5D3 level emission and 0.3% K−1 at 225 °C for Eu3+5D1 level emission. [ABSTRACT FROM AUTHOR]

The application of ultraviolet-C light in the field of surface treatment or photodynamic therapy is highly prospective. In this regard, the stable fluorescent silicate SrO-CaO-MgO-SiO2-Pr2O3 glasses able to effectively convert visible excitation on the ultraviolet praseodymium emission were fabricated and examined. An unusual wide-range visible-to-UVC up-conversion within 240–410 nm has been achieved in Pr3+-doped glasses, revealing their potential advantage in different sophisticated disinfection technologies. The integrated emission intensity was studied as a function of light excitation power to assess a mechanism attributed to UVC luminescence. Especially, it was revealed that the multicomponent silicate glass qualities and praseodymium 3PJ excited state peculiarities are favorable to obtaining useful broadband ultraviolet up-converted luminescence. The glass dispersion qualities were determined between 450–2300 nm. The impact of praseodymium concentration on Vis-NIR spectroscopic glass qualities was evaluated employing absorption spectra, emission spectra, and decay curves of luminescence associated with two involved praseodymium excited states. Especially, efficient interionic interactions can be inferred by investigating the decrease in 1D2 state experimental lifetime in the heavily doped samples. Examination of absorption spectra as a function of temperature implied that excitation at 445 nm should be quite effective up to T = 625 K. Contrary to this, temperature elevation gives rise to a moderate lowering of the visible praseodymium luminescence. [ABSTRACT FROM AUTHOR]

Fluorides have a wide bandgap and therefore, when doped with the appropriate ions, exhibit emissions in the ultraviolet C (UVC) region. Some of them can emit two photons in the visible region for one excitation photon, having a quantum efficiency greater than 100%. In a novel exploration, praseodymium (Pr3+) ions were introduced into KLaF4 crystals for the first time. The samples were obtained according to a high-temperature solid-state reaction. They exhibited an orthorhombic crystal structure, which has not been observed for this lattice yet. The optical properties of the material were investigated in the ultraviolet (UV) and visible ranges. The spectroscopic results were used to analyze the Pr3+ electronic-level structure, including the 4f5d configuration. It has been found that KLaF4:Pr3+ crystals exhibit intense luminescence in the UVC range, corresponding to multiple 4f → 4f transitions. Additionally, under vacuum ultraviolet (VUV) excitation, distinct transitions, specifically 1S0 → 1I6 and 3P0 → 3H4, were observed, which signifies the occurrence of photon cascade emission (PCE). The thermal behavior of the luminescence and the thermometric performance of the material were also analyzed. This study not only sheds light on the optical behavior of Pr3+ ions within a KLaF4 lattice but also highlights its potential for efficient photon management and quantum-based technologies. [ABSTRACT FROM AUTHOR]

Novel ternary fluoro-germano-tellurite (GTS) glasses doped with Er3+ ions with 0.5 mol% and 1.0 mol% were fabricated by a conventional melt and quenching method and investigated using methods of optical spectroscopy. The room-temperature absorption spectrum was recorded and analyzed to determine radiative transition rates, radiative lifetimes, and branching ratios of Er3+ luminescence. Decay curves of Er3+ luminesccence were recorded and analyzed. Temperature dependences of emission spectra and absorption spectra in the region from RT (room-temperature) up to 675 K were studied in detail. The contribution of competing radiative and nonradiative processes to the relaxation of luminescent levels of Er3+ was assessed. Absolute and relative sensitivity were established utilizing the comprehensive model based on thermally coupled 2H11/2/4S3/2 excited states of erbium. The high quantum efficiency of the first erbium-excited state and value of gain coefficient indicate that GTS:Er glass system can be considered as conceivable NIR (near infrared) laser material as well. [ABSTRACT FROM AUTHOR]

Abstract The thermal and optical properties of oxyfluorotellurite (65-x)TeO 2 -20ZnF 2 -12PbO-3Nb 2 O 5 -xSm 2 O 3 (x = 0.5, 2 and 5) glass systems were investigated. Glass thermal stability were monitored by differential thermal analysis (DTA) and adequate thermal stability criteria ΔT, H' and S were determined. It was shown that the thermal stability of the investigated materials increases with the increasing of samarium ions content. The absorption and emission spectra of Sm3+ ions in oxyfluorotellurite glass were recorded in the wide spectral range from UV to NIR. Based on the Judd-Ofelt (J–O) procedure oscillator strengths, phenomenological Judd-Ofelt intensity parameters Ω 2,4,6, radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels were determined. The luminescence decay curves of the 4G 5/2 (Sm3+) excited state were recorded for three different concentrations of Sm3+ and corresponding experimental lifetimes were determined. Photoluminescence emission spectra were measured in the temperature range from 300 K up to 725 K to evaluate the materials under study as luminescent temperature sensor. Highlights • (65-x)TeO2-20ZnF2-12PbO-3Nb2O5-xSm2O3 (x = 0.5, 2, 5 mol%) glasses were prepared. • Thermal properties of glasses were analyzed as a function the Sm3+ concentrations. • The optical properties of Sm3+ ions in oxyfluorotellurite glass were assessed. • The materials under study were evaluated as luminescent temperature sensors. [ABSTRACT FROM AUTHOR]

Abstract Spectroscopic properties of Gd 3 Ga 3 Al 2 O 12 (GGAG) single crystals co-doped with various configurations of (Eu + Tb); (Eu + Ce); (Tb + Ce) and (Eu+ Tb + Ce) ions have been investigated. The effect of distinct Ln3+ co-doping variations on luminescence of garnet crystals was studied using the different excitation wavelengths. The Ln3+-Ln3+ and host-Ln3+ interplays have been considered in doubly and triply doped GGAG:Ln3+. The crystals containing cerium ions are characterized by mainly broadband emission in the 450–750 nm spectral region that is adequately modified in green and red spectral range in the samples co-doped with terbium and europium, respectively. The Eu3+ luminescence in materials under study is selectively excited employing solely f-f europium transitions. Contrary to that, emission of terbium and cerium occur as result of interaction with Gd3+ and adjacent co-dopants. Graphical abstract Image 1 Highlights • Novel doubly and triply - doped GGAG garnet crystals for lighting system applications. • Luminescent and excitation properties of GGAG:Ce,Tb,Eu crystals. • Optimization of phosphor color by various combination of Ce, Tb, Eu dopants. • Evaluation of Ln3+-Ln3+ and host-ion interactions. [ABSTRACT FROM AUTHOR]

Oxyfluorotellurite (65-x)TeO 2 –20ZnF 2 –12PbO–3Nb 2 O 5 –xLn 2 O 3 (Ln = Nd 3+ and Yb 3+ , x = 0.5, 2 and 5) and (65-x-y)TeO 2 –20ZnF 2 –12PbO–3Nb 2 O 5 –xNd 2 O 3 –yYb 2 O 3 (x = 0.5, y = 2 and x = 0.5, y = 5) glass systems were fabricated and their optical and thermal properties were investigated. Absorption and emission spectra of RE admixture ions in oxyfluorotellurite glasses were measured and examined at room temperature in the wide spectral region. Oscillator strengths, phenomenological Judd-Ofelt (J–O) intensity parameters, radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels were determined. Luminescence decay curves of the 4 F 3/2 (Nd 3+ ) and 2 F 5/2 (Yb 3+ ) excited states were recorded and comprehensively analyzed for the single-doped Nd 3+ and Nd 3+ –Yb 3+ co-doped samples. Relaxation dynamics of luminescent levels were studied as a function of the Nd 3+ and Yb 3+ concentrations. An effective non-resonant phonon assisted energy transfer from neodymium to ytterbium was observed and studied. It was found that good thermal stability combined with proper spectroscopic parameters of examined Nd, Yb-doped oxyfluorotellurite glasses imply the suitability of these materials for the design of NIR-emitting efficient optical devices. Furthermore, the ability of the Nd 3+ ions in oxyfluorotellurite glass host as luminescent temperature sensor was verified. Relative intensity ratios of neodymium transitions originated in 4 F 7/2 / 4 F 3/2 and 4 F 5/2 / 4 F 3/2 thermally coupled closely-located excited states have been adequately determined and studied. [ABSTRACT FROM AUTHOR]

The electron absorption-, photoluminescence- and electron paramagnetic-resonance spectra of Mn3+ in red beryl from Wah Wah Mountains (Utah USA) and of pink- and purple vesuvianite from Jeffrey Mine (Asbestos, Canada) were measured at room- and low temperatures. The crystal field stabilization energies are equal to 130.9 kJ/mol for the red beryl, and 151.5-158.0 and 168.0 kJ/mol for for the pink- and the purple vesuvianite, respectively. The red photoluminescence of Mn3+ was not intensive either at room- or at low temperatures. The high Mn content in the crystals caused the emergence of an additional emission band and short photoluminescence-decay lifetimes. The latter are only 183 μs for beryl and 17 μs for vesuvianite. [ABSTRACT FROM AUTHOR]

Oxyfluoride glasses doped with erbium and ytterbium have been fabricated at T = 1460 °C. To prepare glass-ceramic systems, the precursor glasses were annealed at temperature 750 °C for 2 h. The ordered fluoride-like crystalline phases were recognized applying XRD, SAED and EDS methods. The spectroscopic properties of the glass-ceramic samples were significantly different as compared to those observed in the precursor glass. Particularly, the emission spectra of glass-ceramics are evidence that some of Er 3 + and Yb 3 + ions reside into the ordered environment. Up-conversion phenomena attributed to visible anti-stokes emission of Er 3 + has been observed under excitation of Yb 3 + ions by a 980 nm diode laser. Especially, the substantial enhancement of red up-converted luminescence was observed in the glass-ceramic system. Dissimilar spectral characteristic and relation of both aforementioned emissions examined in glass and glass-ceramic samples point at different contributions of processes relevant to up-conversion phenomena. The detailed analysis of the crucial Er 3 + and Yb 3 + excited states relaxation dynamics and their spectroscopic qualities has been performed to determine the mechanisms which lead to conversion of the infrared excitation into visible emission. [ABSTRACT FROM AUTHOR]

Highlights: [•] LGT:Er single crystals obtained by Czochralski method. [•] Analysis of absorption and emission spectra as well as decay curves of luminescence. [•] Influence of the temperature on the LGT:Er spectroscopic properties. [•] Spectroscopic evaluation of the LGT:Er potential laser qualities. [ABSTRACT FROM AUTHOR]

Highlights: [•] Samarium doped langatate crystal was grown by Czochralski method. [•] Thermal dependences of Sm3+ emission and absorption have been measured. [•] Judd–Ofelt analysis was carried out and radiative transition rates were calculated. [•] Inhomogeneous broadening of spectral lines has been observed. [ABSTRACT FROM AUTHOR]

Single crystal of LaGaTaO (LGT) containing intentionally 0.5 % of Ho and 1 % of Yb was grown by the Czochralski method. Examination of chemical composition of the grown crystal revealed that luminescent holmium and ytterbium ions are preferably retained in the melt and their actual concentrations are 0.12 and 0.24 %, respectively. Spectroscopic investigation performed encompassed IR host absorption spectra and Raman spectra at room temperature, optical absorption and luminescence spectra of Ho and Yb at room temperature and at 5 K, and luminescence decay curves at room temperature. It was found that all spectral bands recorded show important inhomogeneous line broadening. This feature was attributed to structural disorder inherent to the crystal lattice in which pentavalent Ta ions occupy octahedral Ga(1) sites together with trivalent Ga ions. Despite small concentrations of luminescent ions, the occurrence of nonradiative interaction that feeds the I and I levels of Ho ions by transfer of an excitation from the F level of Yb ions was evidenced. Based on examination of spectroscopic parameters evaluated, it was concluded that LGT:Ho, Yb may be considered as a potential intermediate-gain laser active material able to emit infrared radiation from the I → I transition of Ho around 2 micrometres upon laser-diode pumping into Yb absorption band. [ABSTRACT FROM AUTHOR]

Abstract: The KGd2F7:Tb and KGd2F7:Tb,Eu samples were obtained using a solid state reaction. Excitation spectra and emission spectra are reported and analyzed within the VUV–UV–vis spectral range. The intense green luminescence is observed in the KGd2F7:Tb while the combined emission of terbium and europium in the KGd2F7:Tb,Eu covers substantially the region of white light. The materials under study can be effectively excited making use of intense f–d transitions of Tb3+ in the VUV–UV region. Experimental lifetimes of luminescent levels have been measured and discussed. It was found that the considerable energy transfer from Tb3+ to Eu3+ occurs. [Copyright &y& Elsevier]

A series of the Tb- and Dy-doped glasses with Li2O--2B2O3 (or Li2B4O7:Tb and Li2B4O7:Dy) composition were synthesised and their spectroscopic properties were investigated. The Li2B4O7:Tb and Li2B4O7:Dy glasses of high chemical purity and optical quality were obtained from corresponding polycrystalline compounds in the air using standard glass technology. The Tb and Dy impurities were added to Li2B4O7 composition in the form of Tb2O3 and Dy2O3 oxide compounds in amounts of 0.5 and 1.0 mol%. The electron paramagnetic resonance (EPR), luminescence excitation and emission spectra of the Li2B4O7:Tb and Li2B4O7:Dy glasses were investigated. On the basis of EPR and photoluminescence spectra analysis it was shown that the Tb and Dy impurities are incorporated in the Li2B4O7 glass network as Tb3+ (4f8, 7F6) and Dy3+ (4f 9, 6H15/2) ions, exclusively. All observed transitions of the Tb3+ and Dy3+ centres in the luminescence excitation and emission spectra were identified. The luminescence kinetics shows single exponential decay for Tb3+ and Dy3+ centres in Li2B4O7 glasses. The lifetime values for main emission transitions of the Tb3+ and Dy3+ centres in the Li2B4O7 glasses containing 0.5 and 1.0 mol% Tb2O3 and Dy2O3 are determined at T = 300 K. Peculiarities of optical properties and local structure of the Tb3+ and Dy3+ centres in the Li2B4O7:Tb and Li2B4O7:Dy glasses as well as their potential applications have been discussed. [ABSTRACT FROM AUTHOR]

Oxyhalide lead borate glasses doped with rare earth ions have been studied before and after thermal treatment. The rare earths as optically active ions were limited to the Er3+ ions. Near-infrared luminescence due to the main 4I13/2-4I15/2 laser transition of Er3+ was registered. The introduction of PbX2 to the borate glass results in a reduction of spectral linewidth and an increase of luminescence lifetime of 4I13/2 state of Er3+ ions. The unusual large spectral linewidth for 4I13/2-4I15/2 transition of Er3+ in the oxide glass host was obtained, whereas the luminescence decay from 4I13/2 state is longer for a sample with PbF2 than PbCl2 and PbBr2. Heat treatment introduces transformation from a glass to transparent glass-ceramic (TGC). The coordination sphere around Er3+ ions is changed, giving important contribution to the luminescence characteristics. The spectroscopic consequence of this transformation is the increase of luminescence lifetime and the narrowing of spectral lines of Er3+. [ABSTRACT FROM AUTHOR]

Optical absorption, luminescence excitation, and emission spectra as well as luminescence kinetics of the Sm- and Yb-doped glasses with lithium tetraborate (Li2B4O7) composition were investigated and analysed. The Sm- and Yb-doped lithium tetraborate glasses of high optical quality were obtained in air from corresponding polycrystalline compounds according to standard glass synthesis technology. The Sm and Yb impurities were added to the Li2B4O7 compound in the form of Sm2O3 and Yb2O3 oxides in amount of 0.4 mol%. Using optical and electron paramagnetic resonance spectroscopy it was shown that the Sm and Yb impurities are incorporated into the lithium tetraborate glass network as Sm3+ (4f5, 6H5/2) and Yb3+ (4f13, 2F7/2) ions, exclusively. All of the observed transitions in the absorption and luminescence spectra of Sm3+ and Yb3+ centres were identified. The luminescence kinetics of the Sm3+ and Yb3+ centres in the Li2B4O7 glass are characterised by a single exponential decay. Decay constants for the main emission transitions of the Sm3+ and Yb3+ centres in the lithium tetraborate glass were obtained at T = 300 K. Incorporation peculiarities and optical spectra of Sm3+ and Yb3+ ions in the lithium tetraborate glass have been discussed in comparison with other borate glasses and crystals. [ABSTRACT FROM AUTHOR]

Abstract: Er3+-doped KCaY(VO4)2 microcrystalline samples were synthesized using a high temperature solid-state reaction technique. Spectroscopic properties of Er3+: KCaY(VO4)2 are studied and the nature of emissions is discussed. A strong green and infrared luminescence were observed under excitation at 314nm in the O2−→V5+ charge-transfer transitions and direct excitation of Er3+ ions at 435nm. A strong emission lines in the blue region are due to the transitions of VO4 3− ions have been observed at 77K. The Judd–Ofelt parametrization scheme has been applied to the analysis of the room temperature absorption spectra in order to evaluate the intensity parameters, the branching ratios and the radiative lifetimes of the 4I13/2, 4I11/2, 4F9/2 and 4S3/2 emitting levels. The effective cross-section has been calculated for the 4I13/2→4I15/2 transition, indicating that the title compounds is a promising active medium for application in the three-level laser system. The up-conversion emission in Er3+: KCaY(VO4)2 was investigated at 300K. The decay profiles of the Stokes and anti-Stokes emissions were measured and the mechanism of up-conversion luminescence is discussed. [Copyright &y& Elsevier]

The cause of the split of 4A4E(4G) Mn2+ excited level measured on minerals spectra is discussed. It is our view that ∆E = |4E(4G) − 4A(4G)| should be considered an important spectroscopic parameter. Among the possible reasons for the energy levels splitting taken under consideration, such as the covalent bond theory, the geometric deformation of the coordination polyhedron and the lattice site's symmetry, the first one was found to be inappropriate. Two studied willemite samples showed that the impurities occur in one of the two available lattice sites differently in both crystals. Moreover, it was revealed that the calculated crystal field Dq parameter can indicate which of the two non-equivalent lattice sites positions in the willemite crystal structure was occupied by Mn2+. The above conclusions were confirmed by X-ray structure measurements. Significant differences were also noted in the Raman spectra of these willemites. [ABSTRACT FROM AUTHOR]

Optical absorption and luminescence spectra as well as luminescence kinetics of the Nd3+ centres in glasses with Ca3Ga2Ge3O12:Nd composition, containing 0.2 and 1.0 wt% of the Nd2O3 were presented and analysed. The oscillator strengths and phenomenological intensity parameters Ωt (Ω2, Ω4, and Ω6) were obtained using standard Judd-Ofelt theory. Calculated Ωt parameters, radiative transitions rates, branching ratios and radiative lifetime for Nd3+ centres in the glass with Ca3Ga2Ge3O12 composition were analysed and compared with corresponding Nd3+ parameters in their crystalline analogue with garnet structure. Experimental lifetimes are compared with those calculated, and quantum efficiency of Nd3+ centres from 4F3/2 emitting level in the glass with Ca3Ga2Ge3O12 composition is estimated. Incorporation peculiarities and local structure of Nd3+ luminescence centres in the glass with Ca3Ga2Ge3O12 composition and corresponding Ca3Ga2Ge3O12:Nd3+ garnet laser crystals are considered. On the basis of extended X-ray absorption fine structure (EXAFS) spectra (L3-edge) of rare-earth elements analysis it has been shown that Nd3+ luminescence centres in the CaO-Ga2O3-GeO2 glass network occupy structural sites with the coordination number to oxygen N = 6. [ABSTRACT FROM AUTHOR]

This paper deals with broadband near-infrared luminescence properties of lead germanate glass triply doped with Yb3+/Er3+/Tm3+. Samples were excited at 800 nm and 975 nm. Their emission intensities and lifetimes depend significantly on Er3+ and Tm3+ concentrations. For samples excited at 800 nm, broadband emissions corresponding to the overlapped 3H4 → 3F4 (Tm3+) and 4I13/2 → 4I15/2 (Er3+) transitions centered at 1.45 µm and 1.5 µm was identified. Measurements of decay curves confirm reduction of 3H4 (Tm3+), 2F5/2 (Yb3+) and 4I13/2 (Er3+) luminescence lifetimes and the presence of energy-transfer processes. The maximal spectral bandwidth equal to 269 nm for the 3F4 → 3H6 transition of Tm3+ suggests that our glass co-doped with Yb3+/Er3+/Tm3+ is a good candidate for broadband near-infrared emission. The energy transfer from 4I13/2 (Er3+) to 3F4 (Tm3+) and cross-relaxation processes are responsible for the enhancement of broadband luminescence near 1.8 µm attributed to the 3F4 → 3H6 transition of thulium ions in lead germanate glass under excitation of Yb3+ ions at 975 nm. [ABSTRACT FROM AUTHOR]

Optical absorption spectra and luminescence spectra were recorded as a function of temperature between 295 K and 800 K for single crystal samples of Gd2SiO5:Dy3+, Lu2SiO5:Dy3+, LiNbO3:Dy3+, and Gd3Ga3Al2O12:Dy3+ fabricated by the Czochralski method and of YAl3(BO3)4:Dy3+ fabricated by the top-seeded high temperature solution method. A thermally induced change of fluorescence intensity ratio (FIR) between the 4I15/2→ 6H15/2 and 4F9/2 → 6H15/2 emission bands of Dy3+ was inferred from experimental data. It was found that relative thermal sensitivities SR at 350 K are higher for YAl3(BO3)4:Dy3+ and Lu2SiO5:Dy3+than those for the remaining systems studied. Based on detailed examination of the structural peculiarities of the crystals it was ascertained that the observed difference between thermosensitive features cannot be attributed directly to the dissimilarity of structural factors consisting of the geometry and symmetry of Dy3+ sites, the number of non-equivalent Dy3+ sites, and the host anisotropy. Instead, it was found that a meaningful correlation between relative thermal sensitivity SR and rates of radiative transitions of Dy3+ inferred from the Judd–Ofelt treatment exists. It was concluded that generalization based on the Judd–Ofelt parameters and luminescence branching ratio analysis may be useful during a preliminary assessment of thermosensitive properties of new phosphor materials. [ABSTRACT FROM AUTHOR]

Responding to the latest trends in luminescence thermometry, a new material of TZPN glass doped with Tb3+ ions was investigated for its use in the single band ratiometric approach. In contrast to the most of the Tb3+ doped phosphors emission intensity of Tb3+ ions in TZPN glass upon excitation matched to transitions from the ground 7F 6 level show strong thermal quenching of luminescence intensity. On the other hand for an excitation line matched to the absorption from the thermally coupled excited 7F 5 level, the emission intensity increases for temperature elevation. The ratio of these two signals is known to be an excellent temperature dependent parameter enabling a highly sensitive temperature readout. Strong thermal quenching of Tb3+ emission was discussed in terms of the thermally induced electron transfer from f state to the conduction band of the glass. In this work, it has been shown that optimization of the thermal quenching process is as important as the previously proposed optimizations of the intensity variability upon stimulation matched to excited state absorption. High relative sensitivities reaching 1–2%/°C were achieved, mainly because of the strong thermal quenching of the luminescence exhibited by the TZPN: Tb3+ glasses with different concentrations of dopant ions. • TZPN glasses doped with Tb3+ ions were applied to luminescence thermometry. • Excitation lines matching GSA and ESA allowed for SBR approach to be applied. • The observed rapid thermal quenching of GSA-excited luminescence was discussed. • Optimizing the GSA-excited emission allowed to achieve high sensitivities. [ABSTRACT FROM AUTHOR]

In this work, spectroscopic properties of europium and erbium ions in heavy metal oxide glasses have been studied. The phonon energy of the glass host was determined based on Eu3+ excitation spectra measurements. Near-IR emission spectra at 1550 nm related to 4I13/2 → 4I15/2 transition of erbium in heavy metal glasses were examined with special regards to luminescence bandwidth and measured lifetime. In particular, correlation between phonon energy and the measured lifetime 4I13/2 (Er3+) was proposed. The luminescence lifetime for the 4I13/2 upper laser state of erbium decreases with increasing phonon energy in glass matrices. Completely different results were obtained glass samples with europium ions, where the 5D0 lifetime increases with increasing phonon energy. Our investigations suggest that the values of measured 5D0 lifetime equal to radiative lifetimes for all heavy metal oxide glasses. [ABSTRACT FROM AUTHOR]

There are many figures of merit, which determine suitability of luminescent thermometers for practical applications. These include thermal sensitivity, thermal accuracy as well as ease and cost effectivness of technical implementation. A novel contactless emission thermometer is proposed, which takes advantage of the coexistence of photoluminescence from Nd3+ doping ions and black body emission in transparent Nd3+ doped-oxyfluorotellurite glass host matrix. The opposite temperature dependent emission from these two phenomena, enables to achieve exceptionally high relative sensitivity SR = 8.2%/°C at 220 °C. This enables to develop new type of emissive noncontact temperature sensors. [ABSTRACT FROM AUTHOR]

Crystals of LiNbO3 single-doped with Sm3+, Tb3+, or Dy3+ and crystal of LiTaO3 single-doped with Tb3+ were grown by the Czochralski method. Luminescence spectra and decay curves for LiNbO3 samples containing Sm3+ or Dy3+ ions were recorded at different temperatures between 295 and 775 K, whereas those for samples containing Tb3+ ions were recorded at different temperatures between 10 and 300 K. Optical absorption spectra at different temperatures were recorded within the UV-blue region relevant to optical pumping of the samples. It was found that the effect of temperature on experimental luminescence lifetimes consists of the initial temperature-independent stage followed by a steep decrease with the onset at about 700, 600, and 150 K for Sm3+, Dy3+, and Tb3+ ions, respectively. Additionally, comparison of temperature impact on luminescence properties of LiNbO3:Tb3+ and LiTaO3:Tb3+ crystals has been adequately described. Experimental results were interpreted in terms of temperature-dependent charge transfer (CT) transitions within the modified Temperature—Dependent Charge Transfer phenomenological model (TDCT). Disparity of the onset temperatures and their sequence were explained based on the location of familiar zigzag curves connecting the ground state levels of rare earth ions with respect to the band-gap of the host. It was concluded also that LiNbO3:Sm3+ is suitable as an optical sensor within the 500–750 K temperature region whereas LiNbO3:Dy3+ offers the highest sensitivity at lower temperatures between 300 and 400 K. [ABSTRACT FROM AUTHOR]

Lead tungstate PbWO4 nanocrystals in transparent lead borate glass-ceramics containing Er3+ ions were fabricated. Luminescence spectra at about 1530 nm due to main 4 I13/2-4 I15/2 laser transition of Er3+ ions were examined for glass samples before and after heat treatment. Near-infrared luminescence of Er3+ ions in glass-ceramics is enhanced and long-lived in comparison to precursor glasses. It suggests that the Er3+ ions are partially incorporated into PbWO4 crystalline phase. [ABSTRACT FROM AUTHOR]

Abstract: Upon UV–VUV excitation terbium doped K5Li2LaF10 emits white light coming from the 5D3 and 5D4 multiplets for content of Tb3+ up to 10at%. For higher concentrations (80 and 100at%) the emission becomes green. In excitation spectrum, recorded at 12K, the positions of the zero-phonon lines are not well determined. The spin allowed f–d transitions in this spectrum are similar to the cerium one in K5Li2LaF10: Ce3+, as van Pieterson proposed in the frames of Dorenbos’ model. The maxima of these terbium f–d transitions are found at: 46,976, 57,124, 59,404, 60,629 and 67,110cm−1. The lowest forbidden, high-spin d band is situated at 39,193cm−1. The lifetime of the 5D4 multiplet is 7.5ms and does not depend on the terbium concentration, but the 5D3 lifetimes are strongly influenced and amount to: 2710, 2130, 14.1, 9.5μs for 2, 10, 80, 100at% of terbium, respectively. This is in agreement with the colour rendering of these samples. [Copyright &y& Elsevier]

Spectra and decay curves of luminescence induced in a single crystal of LiTaO 3 :Pr3+ by femtosecond light pulses at different wavelengths from the UV-Blue and NIR regions were recorded and analyzed. It was found that excited levels involved in the broad UV absorption band of LiTaO 3 : Pr3+ are not able to relax via radiative transitions but they feed nonradiatively excited states of the ground Pr3+ configuration. Femtosecond pulse excitation in the NIR region results in an up-converted visible luminescence weakly affected by the pulse wavelength within the 1200 nm–1800 nm region. Spectra acquired imply that the supercontinuum (SC) generated does not promote single - or double-photon processes that may feed the 3P 0 or 1D 2 levels via transitions within the ground 4f2 configuration. It was concluded that the excitation mechanism is consistent with the multiphoton excitation (MPE) that feeds the 5d levels of Pr3+. • Conversion of femtosecond pulses into optically uniaxial system. • Down and up-conversion phenomena in LiTaO 3 :Pr3+ crystal. • Effect of supercontinuum generation on Pr3+ excited states excitation. • Ultrashort pulses induced change of electrical conductivity. [ABSTRACT FROM AUTHOR]

The color change of the pink and colorless LiAlSi2O6 spodumene crystal due to irradiation and heating is explained. The hypothesis about the change of Mn3+ to Mn4+ after irradiation was rejected. For the studied crystals, it was shown that both Mn2+ and Mn3+ occupy the M2 (not the M1) crystal site. Spodumene crystals which are primary pink (kunzite) contain Mn3+ (and Mn2+) at the M1 site. By contrast, those that become pink due to irradiation and heating contain Mn3+ and Mn2+ at the M2 site. The emission band of the former is 625 nm, and for the latter, it is 591 nm. [ABSTRACT FROM AUTHOR]

Single crystal of La 3 Ga 5.5 Ta 0.5 O 14 (LGT) doped with Dy3+ was fabricated by the Czochralski technique and investigated employing methods of optical spectroscopy. Polarized optical absorption spectra and luminescence spectra were recorded at room temperature. Unpolarized absorption and luminescence spectra were recorded at 10 K. Spectra of blue luminescence related to transitions 4I 15/2 , 4F 9/2 → 6H 15/2 were recorded at several temperatures in the 300–773 K region. Dy3+ ions have the same symmetry sites in LGT but their spectra show inhomogeneous broadening due to structural disorder of the host and are markedly anisotropic. Results of the Judd-Ofelt treatment made it possible to assess emission cross sections for the 4F 9/2 → 6H 15/2 blue luminescence and for the 4F 9/2 → 6H 13/2 yellow luminescence employing Fuchtbauer-Ladenburg formula and reciprocity method. In particular, a spectral distribution of La 3 Ga 5.5 Ta 0.5 O 14 : Dy3+ σ-polarized luminescence band with an emission cross section σ em = 0.51 × 10−20 cm2 at 573.5 nm is favorable for a laser operation in the visible. Interpretation of the effect of temperature on the blue emission spectra leads to the conclusion that La 3 Ga 5.5 Ta 0.5 O 14 : Dy3+ is promising for application as luminescent thermometer. • Novel single crystal La 3 Ga 5.5 Ta 0.5 O 14 :Dy (LGT:Dy). • Detailed analysis of optical spectra and luminescence decay curves. • Potential visible laser operation at 573.5 nm. • Temperature sensitivity of LGT:Dy luminescence. [ABSTRACT FROM AUTHOR]

Using steady-state luminescence measurements, the luminescence spectra of Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Dy3+, Er3+ and Yb3+ for the agrellite sample from the Kipawa River region have been measured. The emission spectra of Eu3+ and Dy3+ next to those of Sm3+ and Pr3+ have been measured for characteristic excitation conditions. The most efficient luminescence activator in the studied sample was Ce3+. This ion was also a sensitizer of Pr3+, Sm3+, Eu3+, and Dy3+ luminescence. [ABSTRACT FROM AUTHOR]

For studied LiAlSi 2 O 6 spodumene crystals, afterglow effect was observed and explained. The luminescence spectra under femtosecond excitation have been presented for this crystal for the first time. The emission bands of point defects in blue, besides those of Mn2+ in orange, have been measured. We demonstrate that emission from defects causes sustaining of emission of Mn2+, and thus, the afterglow phenomenon occurs. The various quantitative ratio of Mn2+ to defects causes the changes in afterglow phenomenon. Image 1 • Lattice defects change color and luminescence intensity of Mn-bearing silicate. • Energy transfer from lattice defects to Mn2+ enhance afterglow effect. • Irradiation changes the mutual contribution of emission from defects and Mn2+. [ABSTRACT FROM AUTHOR]

Terbium ions in Gd 3 Ga 3 Al 2 O 12 (GGAG) single crystal exhibit strong luminescence originated in the 5D 3 and 5D 4 multiplets. The decay time of the 5D 3 state is 1072 μs and 724 μs at 5 K and 300 K, respectively. The time dependence of luminescence originated from the 5D 4 multiplet is consistent with single exponential decay, with lifetime values 3579 μs at low temperature and 2902 μs at 300 K. The non-exponential decay curves have been fitted in the frame of Inokuti-Hirayama model, indicating that the dipole-dipole interaction plays an important role in the fluorescence quenching of the 5D 3 level. The calculated R 0 parameter values are equal to 11.56 Å and 12.86 Å for 5 and K 300 K, respectively. The positions of multiplets up to 40000 cm−1 are determined employing the f-shell empirical programs. CIE 1931 coordinates are x = 0.298 , y = 0.664 (green) at 5 K and x = 0.360, y = 0.538 (yellowish green) at 300 K. • A new material has been obtained in the form of single crystal. • A starting stoichiometry is given to minimize segregation process. • Low temperature positions of 4f and 5d states have been determined. • Energy transfer processes have been examined. • Influence of temperature on the Tb transition ratio has been investigated. [ABSTRACT FROM AUTHOR]

The Y 2-x Te 4 O 11 (x = 0.1, 0.5, 1.0, 2.0 and 5.0 at%) microcrystalline powders were successfully synthesized by a conventional solid state reaction method. Optical absorption (300 K) and fluorescence spectra (300 K) as well as fluorescence decay curves (300 K) of the emitting levels of Tm 3+ ion in Y 2 Te 4 O 11 powders are presented and analyzed in details. The Judd-Ofelt theory was applied to analyze experimental data for the quantitative determination of phenomenological Ω λ ( λ  = 2, 4, 6) parameters, radiative transition probabilities ( A ), branching ratios ( β ) of luminescence and radiative lifetimes ( τ rad ) of the 1 D 2 , 1 G 4 , 3 H 4 and 3 F 4 levels. The observed non-exponential decays nature and concentration quenching of the 1 G 4 and 3 H 4 states have been attributed to cross-relaxation processes and this phenomena has been analyzed by Inokuti-Hirayama model. The stimulated emission cross-section for the 3 F 4 → 3 H 6 transition equals to 1.12 × 10 −20 cm 2 at 1809 nm was calculated using the Füchtbauer-Ladenburg method and compared with the corresponding values of other Tm 3+ -doped laser hosts. From obtained results, follow that the Tm 3+ :Y 2 Te 4 O 11 is a potential candidate for a solid-state laser host operating at 1.8 µm. [ABSTRACT FROM AUTHOR]

Er 3+ /Yb 3+ co-doped lead germanate glasses have been examined for up-conversion luminescence temperature sensors. Up-conversion luminescence spectra corresponding to 2 H 11/2 → 4 I 15/2 and 4 S 3/2 → 4 I 15/2 transitions of Er 3+ are changed with temperature. The fluorescence intensity ratio (FIR) and temperature sensitivity were determined. The maximum sensitivity is found to be 70 × 10 −4 K −1 at T = 550 K in the temperature range of 300–600 K. It suggests that Er 3+ /Yb 3+ co-doped lead germanate glass is promising for optical temperature sensors. [ABSTRACT FROM AUTHOR]

Abstract: Spectroscopic measurements of the calcium niobate CaNb2O6 single crystal doped with samarium ions were performed. Polarized absorption and emission spectra as well as luminescence decay curves of this material were recorded as a function of temperature in the 5–300K temperature region. Analysis of low temperature spectra made it possible to determine energies of crystal field components of Sm3+ multiplets involved in the excitation and luminescence phenomena. Number of crystal field levels derived implies that Sm3+ ions in the CaNb2O6 host are accommodated in several different sites. Radiative lifetime of the 4G5/2 metastable level determined based on the Judd–Ofelt analysis of room temperature absorption spectra amounts to 777μs, a value close to that of luminescence lifetime determined from luminescence decay curve. Energy transfer between the NbO6 group and samarium ions was observed in wide temperature range. Intense luminescence related to the 4G5/2→6H7/2 and 4G5/2→6H9/2 transitions centered at 610nm and 660nm, respectively, combined with strong absorption band near 404nm that matches perfectly the pump light provided by commercial InGaN/GaN diode lasers points at a potential of CaNb2O6:Sm3+ for the design of all-solid-state visible lasers. [Copyright &y& Elsevier]

Abstract: Lead borate glasses were prepared and then heat treated in order to obtain transparent glass-ceramics. Controlled crystallization of precursor lead borate glass at appropriate annealing temperature and time led to formation of the PbWO4 crystallites. The observed broad blue emission band is related to the PbWO4 crystallites. The influence of PbX2 content (X=F, Cl, Br), PbF2 concentration and lanthanide doping (Eu, Dy) on the excitation and emission spectra of lead borate glass-ceramics containing PbWO4 phase was examined. The relationship between Pb–X bond and spectral line width of the blue emission can be successfully observed, when halogen X ions (X=F, Cl or Br) are also present in the distorted PbWO4 crystallites. [Copyright &y& Elsevier]

Spectroscopic and luminescent properties of the Pr-doped and Pr–Ag co-doped borate glasses with Li 2 B 4 O 7 (Li 2 O–2B 2 O 3) composition are studied and discussed. Experimental and theoretical oscillator strengths (f exp and f theor), phenomenological parameters (Ω 2 , Ω 4 , Ω 6), radiative properties (A rad , β , τ rad), and quantum efficiencies (η) of the Pr3+ luminescence were calculated basing on the obtained experimental results and Judd–Ofelt theory. Most intense band of the Pr3+ luminescence is peaked at 601 nm (1D 2 → 3H 4 transition). Presence of the isolated Ag+ (4 d 10, 1S 0) ions, small non-plasmonic Ag aggregates (Ag m n + nanoclusters), and plasmonic Ag metallic nanoparticles in the Li 2 B 4 O 7 :Pr,Ag glass was proposed basing on analysis of the photoluminescence and optical absorption spectra. Observed enhancement of luminescence intensity and increasing of stimulated emission cross-section and quantum efficiency of luminescence in the Li 2 B 4 O 7 :Pr,Ag glass is explained by energy transfer from Ag species to the Pr3+ ions as wells local-field effect induced by Ag nanoparticles. • The Pr-doped and Pr–Ag co-doped Li 2 B 4 O 7 glasses of high optical quality were obtained. • Optical absorption, EPR, photoluminescence spectra and decay kinetics were studied. • Judd-Ofelt parameters (Ω 2 , Ω 4 , Ω 6) and radiative properties (A rad , β , τ rad , σ em , η) were calculated. • Enhancement of the Pr3+ emission intensity in the Li 2 B 4 O 7 :Pr,Ag glass was observed. • Mechanisms of the Pr3+ luminescence improvement in the Li 2 B 4 O 7 :Pr,Ag glass is proposed. [ABSTRACT FROM AUTHOR]

Abstract: Ln-doped oxychloride lead borate glasses were studied using luminescence spectroscopy. Rare earth ions were limited to trivalent Pr3+, Tm3+, Eu3+ and Er3+. Luminescence spectra were registered, which correspond to 3P0–3H4 and 1D2–3H4 transitions of Pr3+, 1G4–3H5 and 1G4–3F4 transitions of Tm3+, 5D0–7F J (J=0, 1, 2, 3, 4) transitions of Eu3+ and 4S3/2,2H11/2–4I15/2 and 4I13/2–4I15/2 transitions of Er3+. Luminescence decays from the excited states of Ln3+ ions were analyzed in detail. The experimental results indicate that relatively high phonon energy of the host gives important contribution to the excited state relaxation of rare earth ions. [Copyright &y& Elsevier]

Abstract: The paper presents the synthesis and spectroscopic properties of 46PbO:53P2O5:Ln2O3 glasses, where Ln=Sm or 0.1Sm+0.9Gd. The glasses show intense luminescence dominated by the orange 4G5/2 → 6H7/2 transition. The luminescence branching ratios and quantum yields have been computed using the Judd–Ofelt analysis of relevant absorption spectra and the observed luminescence lifetimes; the maximum found quantum yield was 69%. The lifetimes and the quantum yields depended on the time of heating the samples at high temperature and on the samarium concentration. [Copyright &y& Elsevier]

Abstract: Good optical quality U3+-doped PbCl2 single crystals of the composition Pb0.99U0.01Cl2 have been obtained by the Bridgman–Stockbarger method. Luminescence spectra of the crystals were recorded in a wide spectral range at room and liquid nitrogen temperatures, and are discussed. Strong infrared emission was observed under 514nm laser pumping to the 5f26d1 bands. The lifetimes of the emitting levels in the visible and near infrared region are given. [Copyright &y& Elsevier]

[Display omitted] • New compound 2-methyl-3,5-dinitro-6-(2-phenylhydrazinyl)pyridine was synthesized. • Its structure was studied using XRD, NMR, IR and Raman methods. • Electron absorption and emission spectra with femtosecond excitation were measured. • The experimental results were analysed in terms of DFT and NBO calculations. • The depopulation mechanism of electron excited states was proposed. A new methyl-dinitro-phenylhydrazinyl-pyridine derivative [2-methyl-3,5-dinitro-6-(2-phenylhydrazinyl)pyridine] was synthesised and characterised by means of structural and spectroscopic measurements. The X-ray diffraction studies revealed that the compound crystallises in the centrosymmetric monoclinic space group P 2 1 / n , with two symmetry-independent molecules in the asymmetric unit with Z = 8. Hydrazo bridge C-NH-NH-C links two fragments composed of phenyl ring and pyridine unit substituted with methyl and nitro groups. Such a structure was confirmed by 1H and 13C NMR studies as well as IR, Raman, UV–Vis, and emission spectra. The results were analysed using the quantum-chemical DFT calculations. The paper reports the vibrational characteristics and discusses dynamical properties of this moiety. The full set of the normal modes typical of the hydrazo bridge was identified and assigned to respective IR and Raman bands. The results of structural and spectroscopic studies were used to find the dependence between the conformation of the θ–NH-NH-ϕ system and its optic properties. The experimental UV–Vis and emission spectra were discussed in terms of the calculated singlet and triplet states that allowed assigning the unique spectral pattern originating from the electrons of the hydrazo-bridge system. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new compound 2-[(4-nitropyridine-3-yl)amino]ethan-1-ol N-oxide was synthesized. • Its structure was studied using XRD, IR and Raman methods. • Electron absorption and emission spectra with femtosecond excitation were measured. • The experimental results were analyzed in terms of DFT and NBO calculations. • The depopulation mechanism of electron excited states was proposed. A new nitropyridine amino N-oxide derivative 2-[(4-nitropyridine-3-yl)amino]ethan-1-ol N-oxide was synthesized and its structural and optical properties were described. Its structure obtained from the X-ray diffraction (XRD) studies was related to the Infrared spectroscopy (IR), Raman spectroscopy (RS), electron Ultraviolet–Visible spectroscopy (UV–VIS) and emission spectra measurements. The experimental results were analyzed in terms of theoretical data obtained from quantum chemical Density Functional Theory (DFT) and Natural Bond Orbital (NBO) calculations. The 6-311G(2d,2p) basis set with the B3LYP functional was used to discuss its optimized structure and vibrational properties. Femtosecond excitation was used to recognize the depopulation mechanism of the electron excited states in the studied compound. It was found that the intermolecular interactions strongly influence the physicochemical properties and application of the new nitropyridine amino N -oxide derivative. [ABSTRACT FROM AUTHOR]

Abstract: Transparent glass-ceramics were successfully prepared during controlled heat treatment of lead borate glasses. The PbF2 particles were dispersed into a borate glass matrix which was evidenced by X-ray diffraction analysis. The phase identification revealed that crystalline peaks can be related to the orthorhombic PbF2 phase. Green up-conversion luminescence due to the 4S3/2–4I15/2 transition of Er3+ ions was registered. In comparison to the precursor glass the luminescence intensity was considerably higher, whereas the luminescence linewidth slightly decreased in the studied oxyfluoride transparent glass-ceramics. It indicated that apart of the trivalent erbium was incorporated into the PbF2 crystalline phase. [Copyright &y& Elsevier]

Until now, only the colourless crystals of mineral afwillite, Ca 3 (HSiO 4) 2 ·2H 2 O, were known from several localities around the world. Present work focuses on blue afwillite counterparts from the Ma'ale Adummim locality in Palestine. Using the wide spectrum of analytical methods we attempted to identify the causes of this unusual colour. Structural investigation confirms the presence of two tetrahedral SiO 3 OH units connected by hydrogen bonds. The Raman spectrum of afwillite, obtained for the first time, shows the increased number of bands in the range of 785-970 cm-1, whose assignation was correlated with the presence of two different kinds of structural units: (SiO 3 OH)3- and its deprotonated counterpart (SiO 4)4-. The heating process at 250 °C, in addition to the colour changes from blue to pastel green, shows the intensity reduction and disappearing of some Raman bands attributed mainly to SiO 3 OH units. The IR investigation confirms also the presence of that unit and provides information that the position and designation of infrared bands above ∼2300 cm-1 is related to the strength of hydrogen bonds within the structure. The stretching and bending OH vibrations of afwillite sample show the partial shift to the lower spectral frequencies after the H/D isotopic exchange in OH or H 2 O groups. Based on the results of the electron absorption and luminescence analyses it has been proposed that the blue colour of afwillite is caused by hole oxygen defect, most probably SiO 3 -. Image 1 • The explanation of the blue colour of afwillite crystals using a wide spectrum of spectroscopic methods. • IR and Raman data of blue afwillite before and after the heating experiment. • Description of structural modification associated with oxygen atoms, hydroxyl group and water molecules. [ABSTRACT FROM AUTHOR]

• New methyl-nitropyridine thione and its thiol tautomer was synthesized. • Crystal structure was determined. • IR and Raman spectra were measured and analyzed using DFT approach. • Electron absorption and emission spectra were studied. • Depopulation mechanism of the electron excited states was proposed. Theoretical and experimental studies of new 4-methyl-3-nitropyridine-2-thione and its thiol tautomer were synthesized and characterized by means of structural and spectroscopic studies. X-ray diffraction, IR, Raman, UV–VIS and emission spectra were measured and analyzed. The quantum chemical DFT calculations were applied in the analysis of the obtained results. The effect of the temperature change on the structural and spectroscopic properties was studied. The vibrational characteristics and dynamical properties of the ϕ-S-H and ϕ= S type compounds are discussed where ϕ is a heterocyclic ring. The results of structural and spectroscopic studies were used to find a diagnostic tool on the structure of thione and tiol forms and their optic properties. [Display omitted] [ABSTRACT FROM AUTHOR]

Green and red up-conversion luminescence spectra corresponding to 2 H 11/2 , 4 S 3/2 → 4 I 15/2 and 4 F 9/2 → 4 I 15/2 transitions of Er 3+ ions in Er 3+ /Yb 3+ co-doped lead-free fluorogermanate glasses have been examined as a function of Yb 3+ concentration and temperature. The green-to-red luminescence intensity ratio diminishes with increasing Yb 3+ concentration. The luminescence intensity ratio for bands related to the 2 H 11/2 → 4 I 15/2 and 4 S 3/2 → 4 I 15/2 transitions of Er 3+ was determined and temperature sensitivity parameters were calculated. The maximal temperature sensitivities for Er 3+ /Yb 3+ co-doped glass samples increase with increasing Yb 3+ concentration and the highest value of 42.5 × 10 −4 K −1 at room temperature was obtained for 0.5Er-3Yb system. Based on gathered data it was concluded that Er 3+ /Yb 3+ co-doped lead-free fluorogermanate glasses are promising for optical temperature sensing. [ABSTRACT FROM AUTHOR]